GB2026537A - An improved method of producing a fibrous mass from peat and means for carrying out the method - Google Patents

Abstract

The present invention relates to a method of producing a fibrous mass from peat. It has not been possible in the past to produce an easily dewaterable fibrous mass from peat when using in the production a continuous process which (1) could be carried out with a minimum amount of manpower, (2) enables a higher yield from the peat moors than had been the case before, (3) enables an efficient separation of colloids and particles smaller than 0.2 mm, and (4) dt enables the use of a simple equipment which, by a quickly made replacement of a screening member, can be changed to match the nature of the dug-up peat. The object of the present invention was to obviate this problem which, according to the invention, is realised substantially by the features that, after a primary sorting operation, the peat-material suspension is liquid-concentration regulated by supplying thereto an amount of liquid depending on the degree of humification of the dug-up peat, and then supplying the suspension under pressure to at least one screening member having a permeability depending on the peat-fibre concentration of the peat-material after said concentration regulation.

Description

SPECIFICATION An improved method of producing a fibrous mass from peat and means for carrying out the method The present invention relates to a method of producing a fibrous mass from peat, comprising carefully exposing the fibres of the peat-fibre material and transferring the same into a peat-material suspension which is subjected to a grading (or: screening, classifying, assorting) operation.

It has not been possible in the past to produce an easily de-watered fibrous mass from peat, while using in the production a continuous process which (1) could be carried out with a minimum of manpower requirements, (2) enables a greater yield from the peat-moors than had been the case before, (3) enables an efficient separating out of colloids and particles less than 0.2 mm, and (4) enables the employment of a simple installation which, by a quickly made replacement of a screening member, can be changed to match the character of the digged-up peat.

The present invention has for its object to obviate these problems, and this, according to the invention, is mainly realized by the fact that, after a primary sorting step, the peat-material suspension is subjected to a liquid concentration (or consistency) regulation by supplying thereto an amount of liquid depending on the degree of humification of the digged-up peat, and then supplying the suspension under pressure to at least one screening member having a permeabiiity depending on the peat-fibre concentration of the peat-material suspension after said concentration regulation.

The present invention has also for its object to provide simple means for carrying out the abovedescribed process. This object is effected by the features disclosed in claim 5 of the appended patent claims.

The invention method will be described more in detail hereinafter with reference to the accompanying drawing which is a diagrammatic illustration of a plant for producing a fibrous mass from peat. The diagrammatically illustrated plant comprises a carriage 1 or the like which can be moved on a peatmoor. The carriage 1 carried a pump 2 having at least one spray nozzle (not shown) emitting a water jet for defibrating peat material on the moor. The pumpable peat material suspension thus obtained (having a peat-fibre concentration of 1 to 6% by weight) is taken up by means of a take-up pump 3 and is conveyed by the latter through a conduit 4 to a primary sorting assembly 5 comprising, for example, at least one rotary, perforated screen having a central intake for the incoming stuff, or inject.In the primary sorting assembly 5, material greater than about 10 mm in size is separated, involving that about 10 to 20% of the peat material of the suspension is separated out (through conduit 6 in the drawing). The material separated out (i.e. the rejected stuff, or reject) has a peat fibre concentration of about 6% and is suitable, for example, for burning or for soil-improvement purposes.

The accepted stuff, or accept, obtained after the primary sorting assembly 5 is a suspension with pumpable consistency because a very small proportion only of the liquid has been removed in the primary sorting assembly 5. This suspension, which contains fibre particles smaller than about 10 mm, including colloides and particles smaller than 0.2, is passed through a conduit 7 to a liquid supplying assembly 8 comprising, for example, a collecting tank with a water inlet 9.

In the liquid supply assembly 8 a liquid, suitably water, is supplied in an amount such as to impart to the peat material suspension a peat-fibre concentration less than 1% by weight. The higher degree of humification of the peat-material of the moor, the more water is supplied in order to obtain a lower peat-fibre concentration.

From the table below it will be seen what peat-fibre concentration is aimed at by supplying water at different degrees of humification (H) of the raw peat material from the moor: Degree of Humification (H) Water supplied in the Water as measured on the peat Supply Assembly to reach the moor: following peat-fibre concen- tration of the suspension: 0 to 3 max about 1% by weight 3 to 6 max about 0.75% by weight above 6 max about 0.5% by weight The consistency regulated peat-fibre suspension, which thus has a peat-fibre concentration lower than about 1% by weight, is supplied through a conduit 10 to an assembly 11 for separating colloids and particles smaller than about 0.2 mm. This assembly 11 comprises for instance a screening member having through-flow perforations about 1 mm in diameter, or smaller.

The size of the through-flow perforations of the screening member of the assembly 11 is determined in relation to the concentration of the suspension and the degree of humification of the peat material.

The more humified peat in the suspension and the lower its concentration, the smaller the perforations of the screening member should be in order to obtain the greatest possible yield of accept, i.e. the maximum possible amount of easily drainable peatfibre material.

From the following table it is seen what yield of easily drainable peat-fibre mass can be obtained at various degrees of humification, various peat-fibre concentrations and various perforation or mesh sizes of the screening member of the assembly 11: Degree of Peat4ibre humification (H) Peat-fibre Hole or mesh (according to concentration size of screen Yield % von Post's scale) in % by weight size of screen 0-3 0.75 - 1 about 1 about 90 3-6 0.5 -0.75 0.5 - 1 about 80 - 90 above 6 0.1 -0.5 max 0.5 about 70 - 90 fine-mesh net or cloth It is seen from this table, that it is possible to obtain a very yield (i.e. usable proportion of the completely treated peat), independently of the degree of humification of the peat moor simply by supplying a suitable amount of water to obtain a suitable peat-fibre concentration, and by using in the assembly 11 a screening member having an adequate hole or mesh size.

At a peat fibre concentration in excess of about 1% by weight and a larger mesh size of the screening member than 1 mm, an essentially lower yield will be obtained, and at higher peat-fibre concentrations and constant mesh size, for example, there will be a great danger of clogging the plant, resulting in a breakdown of the operation of the mill.

By utilizing in the process the values listed in the last-mentioned table, a peat-fibre concentration increase of at least 100% will be obtained in the assembly 11, involving that about 50% of the water supplied is removed, thereby removing also at least 50% of the colloids and particles smallerthan about 0.2 mm (through the conduit 12, possibly for returning to the moor).

The peat-fibre concentration of the suspension after the assembly 11 has a maximum of about 2% by weight, and the suspension now has a character such that it can be passed (through a conduit 13) to and received by take-up assembly 14 comprising an ordinary take-up filter, whereby the peat-fibre concentration can be increased in a simple way to about 10% by weight, and, in addition, at least 75% of the remaining colloids and particles smaller than about 0.2% are carried away with the effluent water (which flows away through the conduit 15, possibly for returning to the moor). The accept stuff obtained is carried away through a conduit 16 to be used, for instance, for papermaking, as a substance for cleaning purposes, for increasing the dry substance content of various reject stuffs, as a fuel or as a soil improvement substance, or fertilizer.

Thus by utilizing the method described, a peat-fibre concentration increase from lowerthan 1% by weight to about 10% by weight will be obtained. In practicing the production method of the invention, of course, more than one primary sorting assembly or unit 5 and more than one secondary sorting assem bly or unit 11 can come into use.

It is advantageous to add the water (or other suit able liquid) after the primary sorting unit 5. It is essential that the water supplied through the conduit from the water supply unit is devoid of suspended particles. In other words: it is not suitable to use water directly from the peat moor, but this water will have to be cleaned from suspended particles, since otherwise the effect of the following separation pro cess would be reduced.

To provide an extremely simple equipment for carrying out the method of the invention, the primary sorting unit 5 comprises a screening member, preferably in the form of a rotary drum 5a with perforations 5b of a diametrical size of about 10 mms. The peat-material suspension is passed into this drum by the conduit 4, the rejected stuff being passed out from the drum 5a through the conduit 6, while the accept stuff is obtained by retaining the suspension passing through the perforations 5b. This accepted stuff is carried away through the conduit 7 and through the liquid supply unit 8 after supplying liquid through the conduit 10 to the secondary sorting unit 11.The latter comprises at least one stationary screening member 11 a having perforations or holes 11 b the sizes of which can vary as stated in the table referred to hereabove. In the present case the portion of the suspension which cannot pass through the screening member 11 a is retained as accepted stuff and is passed furtherthrough conduit 13, whereas the portion of the suspension passing through the screening member 11 a is removed as rejected stuff through conduit 12.

Peat material treated according to the inventive method, and preferably with the employment of the inventive equipment, can, without any difficulties, by mechanical drainage and without any supply of heat have imparted to it a peat-fibre concentration of about 40 to 45% by weight.

The sorting or classifying operation can comprise more than one primary sorting step and more than one secondary sorting step. The primary and secondary sorting steps may be carried out in one single sorting or classifying unit, for instance at different positions in one single screening assembly.

The circuitry of the plant may be provided with or replaced by pressurized elements (not shown and not described in detail, since pressurizing elements of any type previously known to those skilled in the art may be used) to supply the diluted suspension under pressure to the screening unit 11 (preferably being a so-called arcscrnen).

It may be mentioned, finally, that the expression "particles smaller than about 0.2 mms." involves particles which totally are of sizes smaller than 0.2 mms, but preferably also particles whose smallest outer measures are about 0.2 mm, but whose largest outer measures may be larger. Thus, for instance, a particle comprised by this conception may have a length substantially largerthan about 0.2 mm, but a width less than about0.2 mm.

von Post's scale is described in: "Planeringsrapport,TorviSverige 1977:1", a planning report made by the "Namnden for Engeriproduktion:s Planning Board for Peat".

The suspension effluent through conduit 12 and/or conduit 15 and containing organic materials (predominantly colloids and particles smaller than 0.2 mm) from the peat-moor, which remain after the primary sorting step and the fibre separation follow ing thereafter, is subjected to a separation process in which the organic matter is separated out from the fibre-free suspension, after which the dry-substance content of the organic matter is increased by dewatering the same. The organic matter thus dewatered, after storage and/or transport may suitably again be mixed with water to be spread out over a ground area, for instance, to serve as a soil melioration agent and/orto form a covering layer serving, i.e., to preserve humidity in the underlying soil.

The organic matter is suitably separated out of the fibre-free suspension by a sedimentation process, the sedimentation being brought about by causing the peat-fibre concentration of the peat-material suspension to be less than about 0.5% by weight when the degree of humification of the digged-up peat is higher than 6 according to von Post's scale. In the last sedimentation step it may be suitable to add a flocculent, preferably a polymer, alum or other salts, in order to accelerate the sedimenting effect.

The separation of organic matter from the fibrefree suspension may suitably be carried out in a plant of the type shown in Fig. 3. This plant comprises a settling basin 17 into which the fibre-free suspension is supplied through the conduit 12 and/or 15. In this settling basin the organic matter is allowed to settle to the bottom, and the water, in a well-known manner, is allowed to flow off at the top edge of the basin 17 and is carried away through gutters or chutes 18. The organic matter collected in the bottom portion of the basin 17 is pumped by a pumping equipment 19 through a conduit 20 into a second settling basin 21, the pumped suspension containing 4 to 10% dry substance by weight, preferably 5 to 7% dry substance.In order to obtain efficient sedimentation, the settling basin 21 is provided at its top with laminae 22 arranged in a manner pre viouslyknownperse over which water can pass before flowing over the top edges ot the basin 21 to be passed away in a purified state through effluent channels 23. In order to accelerate the sedimentation efficiency in the basin 21, a flocculating agent, for instance a polymer, alum or other salts may be supplied from a storage 24 to increase the weight of the organic particles so that they will sink at a greater velocity. The organic matter collected in the bottom portion of the basin is pumped out from the basin 21 by a pump equipment 25, and the pumpable suspension is furnished through a pipe line 26 to a dewatering station 27.At this station the suspension is dewatered, for instance by a pressing and/or centrifuging process, until the accepted stuff, the accept, has a dry-substant content of at least 10% by weight and up to 25% dry substance. The high drysubstance content now obtained has the advantage that the accept (shown as a block and designated by 28) will be handy, that it can be stacked in a spacesaving manner without any need of particular storage equipments, and that it can be transported at low cost for further use.

The material blocks 28 are conveyed in their "dry condition" to a utilization area 29 where it is mixed with water so as to be spread out together therewith.

At the utilization area 29 the blocks 28 may be supplied into a container 30 with water in which the blocks 28 readily dissolve. The container 30 is connected through a conduit 31 to a water-carrying conduit 32 of a conventional irrigation plant 33, whereby organic - matter - containing water will be drawn up by ejector action from the container 30 and supplied to the stream of water flowing in conduit 32. The water admixed with organic matter is sprayed through nozzles 34 over a field 35 and is deposited as a thin film 36 on this field. When this film has dried, it may be continuously tight if the concentration of organic matter is maintained sufficiently high. The film 36 thus formed may be utilized for preventing wind erosion and for preserving humidity in the underlying soil.It further has soil-melioration properties and thus can be used as a soil melioration agent, in which case it is mixed with the organic dry-substance in a manner to cause 10 to 209 dry'- substance to be spent on each square meter of the field surface. The film also is well adapted to coat sown seeds, particularly when they lie superficially and are especially sensitive during the germination period.

In order to increase the dry-substance content of the accept-stuff obtained from the separation process, the latter may have dry-substance 37 added to it, for instance peat-substance from the same peat moor 38 from which the peat fibres, too, have been taken. Said dry-substance 37 may be added instead of pressing and/or centrifuging or in combination therewith.

Portions of the dewatered accept stuff can be used for producing material for combustion purposes or for lubrication purposes, or as raw materials for chemical industry or as additives in casting.

The separation process described hereinbefore is suitably a sedimentation process, but other methods for separating the organic material can also be applied. The different stages and units of the plant illustrated in Fig. 3 can be varied within wide limits without departing from the general scope of the invention.

The inventive methodology implies the advantage that not only the peat fibres, but also smaller particles are made use of so that the peat-fibre extraction will only reject roots and other larger components of the peat moor and pure or substantially pure water.

These remnant products may be disposed of (for example returned into the peat moor) without any danger of interference with the natural environment.

Claims (9)

1. A method of producing a fibrous mass from peat, in which the fibres of the peat material are exposed and transferred into a peat-material suspension, characterised in that, after a primary sorting operation, the peat-material suspension is liquid-concentration regulated by supplying thereto an amount of liquid depending on the degree of humification of the digged-up peat, and then supplying the suspension under pressure to at least one screening member having a permeability depending on the peat-fibre concentration of the peat-material after said concentration regulation.

2. The method of claim 1 characterised in that the peat-fibre concentration of the peat-material sus pension is caused to be lowerthan about 1% by weight by supplying said liquid in the liquid concent ration regulation.

3. The method of claim 1 or 2 characterised in that the peat-fibre concentration of the peat-fibre material suspension is caused to be lower than about 0.75% by weight when the degree of humification of the digged-up peat according to von Post's scale is 3 to 6.

4. The method of claim 1 or2 characterised in that the peat-fibre concentration of the peat-fibre material suspension is caused to be lower than about 0.5% by weight when the degree of humification of the digged-up peat according to von Post's scale is higher than 6.

5. The method of any of the preceding ciaims 1 to 4 characterised in that a fibre-free suspension obtained by removing fibres from the peat-material suspension is subjected to a separation process in which organic matter, such as colloids and particles smaller than 0.2 mm, remaining in the suspension after removal of the fibres, are separated out of the fibre-free suspension, after which the dry-substance content of the organic matter separated out in the separation process is increased by dewatering the latter.

6. The method according to claim 5 characterised in that, after storage and/or transportation, the dewatered organic matter is again mixed with water in order to be spread out, for instance over a field, to serve as a soil melioration agent and/or for forming a covering layer, i.e. to serve as a humidity preserving layerforthe underlying soil.

7. The method of claim 5 or claim 6 characterised in that the organic matter is separated out from the fibre-free suspension by a sedimentation process, the sedimentation being carried out in at least two steps, viz. a first step in which a suspension containing 4to 10% dry-substance is separated, and a second step in which a suspension is obtained, the drysubstance content of which is increased to 12 to 25% by dewatering.

8. The method of claim 7 characterised in that a flocculating agent, preferably a polymer, is added in the last sedimentation step in orderto accelerate the sedimentation effect.

9. Means for carrying outthe method of any preceding claim of producing a fibre mass from peat, in which the fibres of the peat-material are exposed and transferred into a peat-fibre material suspension, characterised in that at least one screening member (11 a) adapted to receive the pressuresupplied, liquid-concentration regulated peat material suspension, is rigidly mounted and has through-flow perforations (11 b), the size of which is matched to suitthe peat-fibre concentration of the liquid-concentration regulated peat-material sus pension.